The most famous couple in Tenshi Kai history were the two Angels that fell in love. The Saint Something Four belonged to them. Little do they know they were one of the causes of the war between the Tenshi Kai and Akuma Kai. (*sighs* So kawaii!)
And how can we forget the romance that brought us our kawaii little Momoko? I'm sure Momoko's father considered Celeste an angel in his eyes, yet he didn't really know that she was truly an angel.
Yanagiba and Yuri have gotta be the most perfectly matched couple on the show. They're both polite and quiet. I don't know much on how they get together, but I'll add more information as it becomes available.
Takuruu and Hinagiku don't really have a real intimate relationship. The basic story of two childhood friends. But I still think they're kawaii in all respects.